All evidence I can find suggests that device ID 0x4c6e is the "secondary" device for the Radeon Mobility 9000/M9. As such it would be an RV250 chip instead of RV280. However, the radeon drm driver doesn't actually handle "secondary" devices. For example, the (non-Mobility) Radeon 9000 with device ID 496e isn't listed. So I believe this specific device ID should be removed from the list. All it currently accomplishes is printing "Fatal error during GPU init" after the driver fails to map PCI BAR 2, which isn't there on these "secondary" devices.
Tested (on OpenBSD) on a FireMV 2400 PCI card, which is essentially two Mobility M9's with a PCI-PCI bridge, and where the two 0x4c6e secondaries on function 1 are paired with 0x4c66 primaries on function 0. Hopefully this diff can be applied to the Linux kernel as well such that we can keep drm_pciids.h in sync between the various OSes.
Thanks,
Mark
diff --git a/include/drm/drm_pciids.h b/include/drm/drm_pciids.h index e973540..2dd405c 100644 --- a/include/drm/drm_pciids.h +++ b/include/drm/drm_pciids.h @@ -74,7 +74,6 @@ {0x1002, 0x4C64, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_RV250|RADEON_IS_MOBILITY}, \ {0x1002, 0x4C66, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_RV250|RADEON_IS_MOBILITY}, \ {0x1002, 0x4C67, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_RV250|RADEON_IS_MOBILITY}, \ - {0x1002, 0x4C6E, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_RV280|RADEON_IS_MOBILITY}, \ {0x1002, 0x4E44, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_R300}, \ {0x1002, 0x4E45, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_R300}, \ {0x1002, 0x4E46, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_R300}, \